1. Field of the Invention
The present invention relates to a method for connection management through a digital interface among digital devices, and more particularly, to a for allocating a channel in devices having a digital interface such as IEEE1394.
2. Description of the Related Art
With the development of digital devices such as a digital television (TV), a digital video cassette recorder (VCR), and a digital set-top box, standards for interfacing the digital devices have been developed. One standard for interfacing the digital devices is the IEEE1394 standard which is disclosed in xe2x80x9cIEEE1394-1995: Standard for a High Performance Serial Bus, (IEEE Standard Press, December 1995)xe2x80x9d.
In addition, in systems connected to each other via a digital interface such as IEEE1394, connection of isochronous bit streams among digital devices is managed by the IEC61883 specification. The IEC61883 specification is disclosed in xe2x80x9cSpecification of Digital Interface for Electronic Audio/Video Equipment, (Part 1, December 1995, HD Digital VCR Conferencexe2x80x9d.
The IEC61883 specification defines an input plug and an output plug as means for inputting and an outputting of a bit stream in a digital device. The input plug and the output plug are controlled by an input master plug register (iMPR), an input plug control register (iPCR), an output master plug register (oMPR), and an output plug control register (oPCR), respectively. Each digital device manages connection by controlling the registers related to the input plug and the output plug.
Types of connections between digital devices include a point-to-point connection and a broadcast connection. In the point-to-point connection which is formed by an output plug, an input plug, and a channel between these plugs, any digital device can establish or overlay a connection. The device which established the connection can subsequently terminate the connection, thereby freeing the resources (e.g., channels and bandwidth) used by the connection. The broadcast connection is divided into a broadcast-in connection and a broadcast-out connection. The broadcast-in connection connects an input plug and channels, and the broadcast-out connection connects an output plug and channels. The broadcast connection can be established by those devices which actually input and output bit streams through the broadcast connection. A device in the network may terminate and free the connection. At this time, connection management including establishing or freeing the point-to-point connection and the broadcast connection is performed using iMPR, oMPR, iPCR, and oPCR registers. A device that wants to be allocated resources or wants to free resources communicates with a device for isochronous resource management (IRM) of the entire network system in order to be allocated resources or to free resources. For example, in order to communicate image data through a broadcast-out connection between a set-top box (STB) and a digital TV (DTV), the STB can establish a broadcast-out connection to a certain channel (for example, channel 63) and the DTV can establish a broadcast-in connection to a certain channel. By doing so, STB and DTV communicate image data through a certain channel as a communications medium.
Presently, a regulations exists regarding the subject of connection establishment, a channel number to be allocated at the time of establishment, a bandwidth to be allocated at the time of establishment, the subject of the freeing operation, and so on. The channel number allocated when a broadcast-out connection is established has a predetermined relationship with a broadcast channel base field of the oMPR. In addition, where a device has a plurality of output plugs, different channel numbers are allocated to output plugs according to the values of the broadcast channel base field of the oMPR. That is, when the value of the broadcast channel base field is 63 (i.e., the bit value is xe2x80x9c111111xe2x80x9d), the same channel number is allocated to output plugs and otherwise, consecutive numbers are allocated to the output plugs.
However, a channel number, which is determined to be allocated according to the regulation, cannot be allocated in some cases. For example, assuming that a device has three output plugs and the value of the broadcast channel base field of the oMPR is 33, a broadcast-out connection needs to be established for output plug 1 when channel number 33 is already allocated to output plug 0. However, since channel number 34 is used by another device, it cannot be allocated to output plug 1. Therefore, there is a problem in that no regulation is prepared for a case where consecutive channel numbers cannot be allocated.
To solve the above problems, it is an objective of the present invention to provide a method for allocating a channel in a device having digital interface such as the IEEE1394, wherein a channel number may be allocated in accordance with predetermined constraints even if the channel number to be allocated is limited by another part and the thus-determined channel number cannot be allocated due to a particular reason.
It is another object of the present invention to provide a method for allocating a channel in a device having a digital interface such as the IEEE1394, in which a channel number for a broadcast-out connection can be allocated in accordance with IEC61883, even if a channel number to be allocated in accordance with IEC61883 specification for a broadcast-out connection cannot be allocated due to a particular reason.
To accomplish the above object of the present invention, there is provided a method, which satisfies a condition, for allocating a channel to a specific output plug, in which a predetermined relationship with the state of a predetermined part of another digital device is set in accordance with a specification related to a digital interface, in a digital device having a digital interface, the method having the steps of (a) calculating a channel number to be allocated to the output plug in accordance with the condition of the digital interface specification; (b) trying to allocate the channel number calculated in the step (a) to the output plug; and (c) in the step (b), allocating the channel number to the output plug if the trial is successfully done, and if the trial fails, receiving an arbitrary channel number; based on the arbitrary channel number, setting the value of the predetermined part in order to satisfy the conditions of the digital interface specification; and allocating the arbitrary channel number.
To accomplish another object of the present invention, there is also provided a method, which satisfies a condition, for allocating a channel to a specific output plug, in which a predetermined relationship with the state of a predetermined field of a specific register of another digital device is set in accordance with a specification related to a digital interface, at the time of establishing a broadcast-out connection in a digital device having a digital interface, having the steps of (a) calculating a channel number to be allocated to the output plug according to the condition complying with the digital interface specification; (b) trying to allocate the channel number calculated in the step (a) to the output plug; and (c) in the step (b), establishing a broadcast-out channel with the channel number if the trial is successfully done, and if the trial fails, receiving an arbitrary channel number; based on the arbitrary channel number, setting the state value of a predetermined field in the predetermined register in order to satisfy the conditions of the digital interface specification; and establishing a broadcast-out connection with the arbitrary channel number.